Linkage for lift trucks



ATTORNEY C S SCHROEDER LINKAGE FOR LIFT TRUCKS- v 3 Sheets-Sheet 1 June 30, 1953 Filed Sept. 4, 1948 June 30, 1953 c SCHROEDER 2,643,894

LINKAGE FOR LIFT TRUCKS Filed Sept. 4, 1948 3 Sheets-Sheet 2 Patented June 30, 1953 LINKAGE FOR LIFT TRUCKS Charles S. Schroeder, Philadelphia, Pa., assignor to The Yale & 'Towne Manufacturing Company, Stamford, Conn., a corporation of Connecticut Application September 4, 1948, Serial No. 47,860

15 Claims.

This invention relates to a truck of the type in which an elevating platform is moved vertically relatively t a lifting head through suitable linkage, for lifting and lowering a load carried by the platform. In one type of truck of this class, the elevating platform is mounted for movement relatively to the lifting head on parallel links extending between the forward end of the elevating platform and the lifting head. At the rear end of the elevating platform there are mounted lifting wheel links adapted for pivotal movement and carrying wheels at one end thereof. Means are provided for rotating the lifting wheel links as the forward end of the elevating platform moves relatively to the lifting head. In this way, movement is imparted to the lifting wheel links to raise and lower the rear end of the elevating platform as the forward end of the elevating platform ,is itself raised and lowered.

As part of my invention, I have conceived the desirability of s connecting certain of the links extending between the lifting head and the elevating platform of a truck of this class as to permit automatic adjustment of the several parts whereby to prevent a binding of the parts in the event they are not manufactured with extreme accuracy and assembled with extreme precision. As a still further feature of my invention, -I have conceived a construction whereby both the forward links and the rear lifting wheel links are readily assembled to the truck, and also removed from the truck whereby to facilitate greatly the initial assembly and the repair or replacement of the parts.

More particularly, as a feature of the invention, I employ a connector mounted on the elevating platform at its forward end, and at each side thereof, this connector being pivotally related to the elevating platform while movable vertically therewith relatively to-the lifting head. Certain of the links connecting the forward end of the elevating platform to the lifting head are pivoted to the connectors and operate through the connectors. Thereby, through the pivotal relationship between the connectors and the elevating platform, it will be perceived readily that the connectors will adjust themselves automatically between the links and the elevating platform to assume a position for the effective operation of the parts with a minimum of friction and binding.

As a still further feature of the invention whereby the broad results outlined are obtained, the rear lifting wheel links are mounted on bearing members that are readily removable for replacement and are readily applied in place when the truck is initially assembled. Therefore, it will be understood, especially after a reading of the specification that follows, that the operating and lifting parts of my truck are readily replaceable and are readily initially assembled, all for the purposes set forth.

I have thus outlined rather broadly the more important features of my invention in order that the detailed description thereof that follows may be better understood, and in order that my contribution to the art may be better appreciated. There are, of course, additional features of my invention that will be described hereinafter and which will form the subject of the claims appended hereto. Those skilled in the art will appr c at at the conception on which my disclosure is based may readily be utilized as a basis for the designing of other structures for carrying out the several purposes of ,my' invention. It is important, therefore, that the claims to be granted me shall be of sufficient breadth to prevent the appropriation of my invention by those skilled in the art.

Referring now to the drawings, Fig. 1 is an elevation and partial section of a typical industrial truck of the class described showing my invention applied thereto. Fig. 2 is a sectional view of the rear end of the truck showing one lifting wheel link and a wheel carried thereby moved into platform elevating position. Fig. 3 is a view looking downwardly at the elevating platform of the truck of Fig. '1, but with the upper covering plate of the platform removed. Fig. 4 is a section taken along lines 4-14 of Fig. 3. Figs. 5 and 6 are sections taken respectively along lines 5-5 and 6-6 of Fig. 3. Fig. 7 is an exploded view of the parts. assembled t the rear end of one side of the elevating platform. Fig. 8 is an exploded view showing the parts assembled at the forward end of one side of the elevating platform.

Referring now more particularly to the drawings, the truck of my invention includes what I term a lifting head l0 and an elevating platform designated generally-by reference numeral H. The elevating platform is of that type formed of two legs united at their front ends, each leg carrying a separate lifting wheel link and lifting wheel adapted to be actuated as the forward end of the elevating platform is raised and lowered relatively to the lifting head l0.

For lifting and lowering the forward end of the elevating platform ll, '1 utilize a bell crank l2 pivoted to the lifting head at [3 and actuated by the ram piston M of a hydraulic ram assembly l5 pivoted at I6 to the lifting head. Bell crank 12 carries a roller I! that operates against a surface ['8 integral with the elevating platform ll. As is well set forth in the prior art, the movement of the bell crank I2 in a clockwise direction about its pivot at l3 by the ram piston l4 will effect the elevating movement of the'platform I l Reversely. the bell crank [2, through the roller I! and the surface is of elevating platform ii, will control the downward lowering movement of the said platform. v

In conformance with the teachings of the prior art, the elevating platform] I is connected to the lifting head H] by a pair of upper parallel links 20. Links 25 are pivoted to the elevating platform at El and to the lifting head at 22; It is customary in prior art trucks to have lower lifting links similar to the upper lifting links and to provide fixed pivots on the elevating platform and lifting headfor the said links. Moreover, itis customary for the upper and lower links to be parallel and therefore to contribute upward parallelogram lifting movement to the elevating platform ii relatively to. the lifting head upon operation of bell crank I2. I depart from the teachings ofthe prior. art only by using a pair of lower links 25 connected in a novel manner to the elevating platform. Onlyone link 2'5 will be described hereinafter as the two links are the same except that they operate in opposed relation.

The link 25 shown best in Figs. 1, 3, 6, and 8 is pivoted at its forward end on a shaft 26 carried by the lifting head Ill. At its other end the link 25 is bifurcated and is bored as at 21 for a shaft 28 that is adapted to rest in opposed bores 29 of a part that I term a connector 30,.and which is well shown in perspective in Fig. 8. This connector is an intermediary between link 25 and the elevating platform, it being understood by those skilled in the artthat normally the link125 would be pivoted directly to the elevating platform through means of a shaft equivalent to the shaft 7 Connector .36 isadapted for assembly to the elevating platform .through bearing ribs 3| welded to the underside of the elevating platform as best shown in Figs. 3 and 8. Ribs 3 I are cut away to form surfaces 32 for ashoulder 33 formed on the connector 38. .Shoulderi33 is applied to the surfaces 32 on thebearing ribs 3| as. is probably best illustrated in Fig. 6. Thereafter, a bearing plate 34 is applied against the shoulder 35 of connector 4 a clevis 42. Clevis 42 has adjustably threaded thereto a rod 43, this rod 43 extending into a second clevis 44 bifurcated as at 45 for pivotal connection at 41 to a lifting wheel link 46, best shown in Fig. 7. It is the function of pin 41 to contribute movement to the rod 43 as the link 25 is moved pivotally incidental to the movement of the elevating platformrelatively to the lifting head. The rod 43, in turn, is'adapted to rotate the lifting Wheel link 45 through pivot shaft 4! actuated by the clevis 44 into which the rod 43 is adjustably threaded.

The rear end of the elevating platform has secured thereto asby welding, a cross support 3B, bearing plate 34 being secured to the elevating manner set forth, and as probably best illustrated in Fig. 6, the connector 3i! is heldassembled to the elevating platform betweenbearing plate. 34 andbearingribs3l. However, co'nnectorBll will be capable of rotation relatively .to the elevating platform, this rotation. allowingan adjustment of the connector asmay be required through its pivotal relation with the link 25 by means of shaft 28. ,Moreover, the bearing plate 34,, fitting as it does about the connector 30, will serve to hold the pivot shaft 28 in assembled relation to the connector, without any additional means.

The bifurcatedend of link 25, in addition to the bores 21,'contains opposed bores cooperable with a pin. whereby to. assemble to the link 25 member as andsupport blocks 49. A hearing memberjil best shown in Fig. 'I, is secured to the crcss support member 88 and the support blocks 49 by a series ofthreaded studs 51 as best seen in Figs. 4 and 5. In this way, the bearing member 55 may be said to form an integral part of the elevating platform when it is secured thereto. Obviously, the mere removal of the studs 51 will allow a removal of the bearing member 50 from the elevating platform.

Bearing member 58 supports a shaft 52 through bores 53, and the lifting wheel link $5 is bored as at 54 so as to be pivotally mounted on the shaft 52. It will be quite apparent that the movement of the lifting wheel link 46 from its position of Fig. 1 to its position of Fig. 2 will be about the shaft 52 carried by the bearing member 50 and will lift the rear end of elevating platform H.

Bearing member 551 is formed with a cam surface 55, which as shown best in Fig. 1, extends downwardly almost to the plane in which are rotatable wheels 55 mounted on the lifting wheel link (#5 through an axle 57. Because of this relationship of the parts, the cam surface 55 will act to ease the truck upwardly into a pallet as is fully set forth in the Quayle application Serial No. 21,347 filed April 16, 1948, which issued as Patent No. 2,498,504 onFebr'uary 21, 1950. It is thus apparent that through the utilization of a removable bearing memberbfi, I am readily able to replace thelifting wheel link 46 or the Wheels 56, and that at the same time, I am able to supply a cam 55 as is necessary where the truck is used in the handling of pallets. I I

The underface of theelevating platform is further equipped with-relatively long support lugs B5 to which forward cam plates 5! may be secured as seen inFigs. 3 and 7. These cam plates '6! function in the same manner as the cam surfaces 55 to cam the truck upwardly into position relatively to a pallet when the truck is used for handling pallets. 1 Y

. Reviewing once again my invention, it will readily be perceived that through the utilization of the connector 36, I am able to relieve my front linkage mechanismof the strains normally presenttrucks of the particular class. Moreover. I make it possible to replace readily the linkage mechanism and I facilitate the initial assembly of the-linkage mechanism to the truck. Through the utilisationof the-removable bearing members 59, it is possible to assemble to the truck the rear lifting 'wheels and the rear lifting wheel; links and to replace and repair-those parts should they be worn or damaged in-service. I believe that the considerable merits of my inyentionand the contribution thereof to the prior art will now be understood by. those skilled in the art-..- Inowclaim;

inge truck .of the class ldescribed, .a lifting head, an elevating platform, a link pivoted atone end to said lifting head, a connector, means pivoting the other end of .said link to said connector, means mounting said connector for swinging movement with said elevating platform on said link relatively to said lifting head, coacting parts through which said connector adjusts itself on said mounting means relatively to said elevating platform and said pivot between said connector and said link,- a rod pivoted to said link, said rod extending rearwardly from its pivot to the rear end of said elevating platform, a lifting wheel link pivoted relatively to the rear end of said elevating platform, and means of connection be tween said rod and lifting wheel link whereby movement of said rod contributes swinging lift movement to said lifting wheel link.

2. In a truck of the class described, a lifting head, an elevating platform, a'link pivoted at one end to said lifting head, a connector, means pivoting the other end of said link to said connector on an axis parallel to the axis of the link pivot to said lifting head, means mounting said connector for swinging movement with said elevating platform on said link relatively to said lifting head while allowing said connector to pivot rela-,

tively to said elevating platform on an axis substantially perpendicular to the plane of said elevating platform, a rod pivoted to said link, said rod extending rearwardly from its pivot to the rear end of said elevating platform, a I lifting wheel link pivoted relatively to the rear end of said elevating platform, and means of connection between said rod and lifting wheel link whereby movement of said rod contributes swinging lift movement to said lifting wheel link.

3. In a truck of the class described, a lifting head, an elevating platform, a link pivoted at one end to said lifting head, a connector, means pivoting the other end of said link to said connector, means mounting said connector for swinging movement bodily with said elevating platform on said link relatively to said lifting head, coacting parts through which said connector rotates on said mounting means relatively to said elevating platform whereby to allow said connector to adjust itself relatively to said elevating platform and said pivot between said connector andsaid link.

4. In a truck of the class described, a lifting head, an elevating platform, a link pivoted at one end to said lifting head, a connector, means pivoting the other end of said link to said connector on an axis parallel to the axis of the link pivot to said lifting head, and means'mounting said connector for swinging movement with said elevating platform on said link relatively to said lifting head, and means whereby said mounting means allows said connector to pivot relatively to said elevating platform on an axis substantially perpendicular to the plane of said elevating platform.

5. In a truck of the class described, a lifting head, an elevating platform, a connector, means mounting said connector on the forward end of said elevating platform for pivotal movement relatively thereto, said connector moving with said elevating platform otherwise as a part thereof, a link pivoted at one end thereof to said connector and at the other end to said lifting head for mountng said elevating platform for upward vertical swinging movement relatively to said lifting head, a lifting wheel link, means mounting said lifting wheel link for pivotal movement relatively'to the rear end of said elevating platform, and means pivotedat one'end to said lifting wheel link and at the other end to said link for rotating said lifting wheel link on its pivot.

6. In altruck of the class described, a lifting head, an elevating platform, a connector, means mounting said connectoron the forward end of saidfelevating platform for pivotal movement on said link relatively to said lifting .head, a lifting wheel link, means mounting said lifting wheel link for pivotal movement. relatively to the rear end of said elevating platform, and means pivoted at one end to said lifting wheel link and at the other end to said link.

7. In a truck of the class described, a lifting head, an elevating platform, a connector, means mounting said connector on the forward end of said elevating platform for pivotal movement relatively thereto, said connector moving with saidelevating platform otherwise as a part thereof, a link pivoted at one end thereof to said connector and at the other end to said lifting head for mounting said. elevating platform for upward vertical swinging movement relatively to said lifting head, the pivot axis of said connector relatively to saidelevating platform being such that said connector adjusts itself to its pivot axis with said link to remove strain from said pivot axis during swinging of said elevating platform on said link relatively to said lifting head.

8. In a truck of the class described, a lifting head, an'elevating platform, a connector, a bearing member for said connector removably secured on said elevating platform and removably mounting said connector on the forward end of said elevatingplatform for pivotal movement relatively thereto, said connector moving with said elevating platform otherwise as a part thereof,

a link pivoted at one end thereof to said connector and at the other end to said lifting head for mounting said elevating platform for upward vertical swinging movement relatively to said lifting head, a lifting wheel link. means mounting said lifting wheel link for pivotal movement relatively to the rear end of said elevating platform, and means pivoted at one end to said lifting wheel link and at the other end to said link.

9. In a truck of the class described, a lifting head, an elevating platform, a connector, a hearing member for said connector removably secured on said elevating platform and removably mounting said connector on the forward end of said elevating platform for pivotal movement relative thereto, said connector moving with said elevating platform otherwise as a part thereof, a link pivoted at one end thereof to said connector and at the other end to said lifting head for mounting said elevating platform for upward vertical swinging movement relatively to said lifting head, the pivot axis of said connector relatively to said elevating platform being such that said connector adjusts itself to its pivot axis with during swinging of said elevating platform on said'link'relatively to said lifting head, a lifting wheel link, means mounting said lifting wheel link for pivotal movement relatively to therrear end of said elevating platform, and means pivoted at one end'to said lifting wheel link and at the other end to said link.

10. In a truck of the class described, a lifting head, an elevating platform, a connector, a hearing member for said connector removably secured on said elevating platform and removably holding said connector against the underside of the. forward end of.said elevating platform for pivotal movement relatively thereto, said connector moving with said elevating platform otherwise as a part thereof, a link pivoted at one end thereof to saidiconnector and at the other end to said lifting head for mounting said elevating platform for upward vertical swinging movement relatively to said lifting head, the pivot axis of said connectorrelatively to said elevating platform being such that said connector adjusts itself to itspivot axis with said link to remove strain from said pivot axis during swinging of said elevating platform on said link relatively to said lifting head.

11. In a truck of the class described, a lifting head, an elevating platform, a link pivoted at one end to said lifting head, a connector, means pivoting the other end of said link to said connector, means mounting said connector for swinging movement with said elevating platform on said link relatively to said lifting head, said means allowing said connector to adjust itself relatively to said elevating platform and said pivot-between said connector and said link, a rod pivoted to said link; said rod extending rearward- 1yv from its pivot to the rear end of said elevating platform, a lifting wheel link, a bearing for pivotally mounting said lifting wheel link removably secured to the underside of said elevating platform; and means of connection between said rod and lifting wheel link'whereby movement of said rod contributes swinging lift movement to said lifting wheel link;

12. In a truck of the class described, a lifting head, an elevatingplatform, a connector, a hearing member forsaid connector removably secured on said elevating platform and removably mounting said connector on the forward end of said elevating platform for pivotal movement relatively thereto, said connector moving with said elevating platform otherwise as a part thereof, a link pivoted at one end thereof to said connector and at the other end to said lifting head for mounting said elevating platform for upward vertical swinging movement relatively to said lifting head, a lifting wheel link, and a bearing for pivotally mounting said lifting wheel link removably secured to the underside of said elevating platform.

13. In a truck of the class described, a lifting head, anelevating -platform, a link pivoted at one end to said lifting head, a connector, means pivoting the other end of said link to said connector on an axis parallel to the axis of the link pivot to said lifting head, means removably securing said connector for movement with said elevating platform on said link, a rod pivoted tosaid link, said rod extending rearwardly from its pivot to the rear end of said elevating platform, a lifting wheel link, a bearing for pivotally mounting saidlifting wheel link removably secured to the underside of said elevating platform, and means of connection between said rod and lifting wheel link whereby movement of said rod contributes swinging lift movement to said lifting wheel link. 7

14. In a truck of the class described, a lifting head, an elevating platform, means pivotally mounting the forward end of said elevating platform on said lifting head for upward lifting movement relatively thereto, a lifting wheel link for the rear end of said elevating platform, a bearing member for said lifting wheel link secured to the underside of said elevating platform, means whereby the upward lifting movement of the forward end of said elevating platform relatively to said lifting head effects a downward swinging movement of said lifting wheel link relatively to said bearing member, and the lower surface of said bearing member being formed as a cam substantially for the purpose described.

15. In a truck of the class described, a lifting head, an elevating platform, a link pivoted at one end to said lifting head, a connector, a shaft pivoting the other end of said link to said connector, means mounting said connector for swinging movement with said elevating platform on said link relatively to said lifting head, said mounting means allowing said connector to adjust itself relatively to said elevating platform and said pivot between said connector and said link, and a part of said mounting means for said connector holding in position the shaft pivoting the link to the connector.

CHARLES S. SCHROEDER.

References Cited in the file of this patent UNITED STATES PATENTS 

